Frequency threshold in the photoelectric effect

In summary, the photoelectric effect exhibits a frequency threshold that is often seen as a challenge to the wave theory. However, this is due to the outdated semiclassical model used in early 20th century physics. The photoelectric effect's behavior can be explained by the quantum theory and there is no time delay in electron emission, even at low intensities.
  • #1
Gerlan Silva
6
0
The existence of a frequency threshold in the photoelectric effect is often regarded as the strongest objection to the wave theory. Because?
 
Physics news on Phys.org
  • #2
Gerlan Silva said:
The existence of a frequency threshold in the photoelectric effect is often regarded as the strongest objection to the wave theory.

Can you give a specific reference that makes this claim?
 
  • #3
PeterDonis said:
Can you give a specific reference that makes this claim?
The effect of the photoelectric effect is not observed below a certain
Frequency threshold is a consequence of a photon energy having to be equal to
or greater than the true work
 
  • #4
Gerlan Silva said:
The effect of the photoelectric effect is not observed below a certain
Frequency threshold is a consequence of a photon energy having to be equal to
or greater than the true work

This isn't what I asked for. I asked for a reference--a link to a textbook or a peer-reviewed paper that makes the claim you say is "often" made.

Plus, it seems like you have answered the very question you asked in the OP. What exactly is the issue you are asking about?
 
  • #5
PeterDonis said:
This isn't what I asked for. I asked for a reference--a link to a textbook or a peer-reviewed paper that makes the claim you say is "often" made.

Plus, it seems like you have answered the very question you asked in the OP. What exactly is the issue you are asking about?
This issue that I posted is Eisberg's quantum physics. P 79
 
  • #8
Gerlan Silva said:
The existence of a frequency threshold in the photoelectric effect is often regarded as the strongest objection to the wave theory. Because?
Why should there be any objection to "the wave theory", whatever you mean by it. If you mean light as an electromagnetic wave, there's certainly nothing to object against it. The photoelectric effect at the level of Einstein's original (and outdated!) paper of 1905 is (as most of macroscopic optics) in the semiclassical approximation, i.e., describing the em. field as classical and the (charged) matter by quantum theory:

https://www.physicsforums.com/insights/sins-physics-didactics/

The description of the photoelectric effect in the above quoted book is outdated and shouldn't be taught in this way anymore in the 21st century (or only in a lecture on the history of science of the early 20th century, before a consistent quantum theory has been formulated)!
 
  • #9
Gerlan Silva said:
The existence of a frequency threshold in the photoelectric effect is often regarded as the strongest objection to the wave theory. Because?

It was thought, at that time {emphasis was for the benefit of @vanhees71 before he gets into a conniption}, that energy in an EM wave can "accumulate" over time, and thus, a photoelectron can be emitted once the surface has acquired sufficient energy.

Einstein's photoelectric effect model indicates that it can't. On the other hand, if the frequency is above threshold, even at extremely low intensity (for a wave, this means at very low amplitude of oscillation), one will get electron emission. This too matches what is predicted by the photoelectric effect model.

So yes, at that time, these two were thought to be inconsistent with the EM wave picture.

Zz.
 
  • #10
vanhees71 said:
Why should there be any objection to "the wave theory", whatever you mean by it.

Please don't get hung up over the OP's phrasing. The reason I asked for a reference is so that we can look at what the reference said, instead of what the OP's paraphrase of the reference said. As far as I can tell, the reference says basically what @ZapperZ said.
 
  • #11
ZapperZ said:
if the frequency is above threshold, even at extremely low intensity (for a wave, this means at very low amplitude of oscillation), one will get electron emission.

I think it's also important that there is no time delay in the emission: as soon as you turn the light on, even at very low intensity, you get a photoelectric current. The "energy in the EM wave accumulates" model would predict a time delay that gets longer as the intensity gets lower.
 
  • Like
Likes vanhees71

1. What is the frequency threshold in the photoelectric effect?

The frequency threshold in the photoelectric effect refers to the minimum frequency of incoming light that is required to eject an electron from a metal surface. This threshold frequency is unique to each metal and is determined by its work function.

2. How does the frequency threshold affect the number of ejected electrons?

If the frequency of the incoming light is below the threshold frequency, no electrons will be ejected regardless of the intensity of the light. However, if the frequency is above the threshold, the number of ejected electrons will increase with increasing frequency and intensity of the light.

3. What happens to the energy of the ejected electrons at different frequencies?

At frequencies below the threshold, the ejected electrons will have zero kinetic energy. As the frequency increases above the threshold, the energy of the ejected electrons will also increase. This is because the excess energy from the incoming light is transferred to the electrons, giving them kinetic energy.

4. Can the frequency threshold be altered?

The frequency threshold is a characteristic property of a specific metal and cannot be altered. It is determined by the work function of the metal, which is the minimum amount of energy required to remove an electron from its surface. However, the threshold can be affected by external factors such as temperature and surface conditions.

5. How is the frequency threshold related to the photoelectric effect?

The frequency threshold is a crucial factor in the photoelectric effect as it determines whether or not electrons will be ejected from a metal surface by incoming light. It also illustrates the particle-like behavior of light, as only photons with enough energy (frequency) can cause the ejection of electrons from a metal surface.

Similar threads

Replies
5
Views
652
Replies
11
Views
1K
Replies
5
Views
1K
Replies
1
Views
616
Replies
10
Views
2K
Replies
2
Views
1K
  • Quantum Physics
Replies
12
Views
746
  • Quantum Physics
Replies
4
Views
880
Replies
5
Views
822
Replies
4
Views
1K
Back
Top